Natural Design Approach Restores Whitney Drain

The most severely eroded downstream portion of the Whitney Drain was improved by reconstructing the channel and armoring its banks with rock and floodplain benches that will help prevent future erosion and naturalize the area. Rock riffle (top) and cross-vane (bottom) structures were used to stabilize the channel by directing flow away from erosion-prone banks.

A little spring planting is all that remains to be completed after decades of planning, design and legal debate over the cost and approach to correct the Whitney Intercounty Drain’s severe erosion. This is long-awaited news for residents of Michigan’s Arenac, Iosco and Ogemaw Counties who have watched the drain’s rushing water swallow property, wash out roads and decimate a once-thriving smelt and steelhead trout population. The $2.9 million improvement project features a wide variety of river restoration and best management practices (BMPs) to stabilize the drain’s channel slopes and bank systems to prevent loss of property and protect roads and bridges. The natural design approach used will reduce erosion and improve water quality and fishery habitat within the drain and the downstream receiving waters of the Saginaw Bay. The Whitney Drain is more than ten miles long and serves a 93,180-acre watershed, 33% of which is in state or federal ownership. The drain falls under the jurisdiction of the Whitney Intercounty Drainage Board, comprised of Arenac County Drain Commissioner (ACDC), Don Prueter; Iosco County Drain Commissioner, Gary Adams; Ogemaw County Drain Commissioner, Michael DeMatio; and the Board Chair representing the Michigan Department of Agriculture, Michael Gregg. In the 1920’s the East Branch of the AuGres River was rerouted through a 3.8-mile cut-off channel named Whitney A Drain to divert large spring runoff flows generated by snow and ice melt conditions. This channel reduced the severity of flooding in the City of AuGres on the north shore of Saginaw Bay. Located along Turner Road in Whitney Township, Arenac County, the channel routed flow in an easterly direction to Lake Huron, outletting at Whitestone Point. Since the 1960s, all flow has been conveyed through the cut-off channel. While the Whitney Drain has functioned adequately throughout the years, it has constantly worked to achieve a state of equilibrium representative of its original length and gradient prior to construction of the cut-off channel. This has led to decades of erosion and down-cutting of the banks and channel. The drain transformed from a narrow, shallow drain that residents remember jumping across, to a high-velocity body of water carving out new boundaries. Portions of the channel valley down-cut over 32 feet and widened to over 150 feet. Stream velocities commonly exceed 4 to 7 feet per second and erosion of the banks and bed is prevalent. The drain became the largest single contributor of sediment transport and deposition into Lake Huron. Traditional drain improvement projects dredge, deepen, and widen a channel to convey more flow. Trees and shrubs are often cleared from one or both banks to reduce in-channel debris and increase drain access. For the Whitney Drain, dredging activities would have further damaged its unstable banks, required additional right-of-way widths and exacerbated erosion problems. In addition, there was widespread interest in protecting or enhancing the recreational and aquatic resources of the drain and surrounding area.

A more natural approach to design and construction was selected by the Board as the most appropriate and cost-effective way to stabilize the drain. Most of the project focused on stabilizing the existing channel in place using a variety of techniques including rock riffles, riprap, very selective log jam and dead tree removals, and native plantings. However, stabilizing the intense problems in the 3.8-mile downstream portion required constructing a new channel with floodplain benches and native plantings.

Between US-23 and Noble Road near the Singing Bridge, 1,650 feet of the existing downstream channel was relocated to the center of the river valley and replaced with a new channel sized to transport the sediment from the watershed. This action was determined to be the best solution for eliminating toe erosion and continual failure of valley side slopes, preventing large accumulations of sediment within the channel and creating a better flowing, more stable outlet for the drain. The constructed channel’s banks, armored with rock and floodplain benches, were created in the remaining areas outside of the channel to further reduce erosion of the valley walls and to naturalize the area. These floodplain areas were dressed with topsoil, seeded, covered with erosion control blanket and planted with native vegetation.

Twenty-three rock riffle structures were placed in the downstream stretch to provide vertical control within the channel, thereby stabilizing the grade of the drain bottom and concentrating the water’s energy and higher velocities over the rock structures. The structures direct water to the center of the channel to prevent erosion of the streambanks and, like natural riffles, provide significant habitat for aquatic organisms. Fish passage was considered to be a very high priority in the design and construction of the riffles.

Rock riprap was used to stabilize excessively steep, actively eroding streambanks located directly adjacent to Turner Road. Due to the conditions found at these sites and the importance of protecting the roadway, riprap was determined to be the best solution. The riprap streambanks were also treated with vegetative plantings to improve their appearance and stability.

Finally, 2 miles of eroded streambank were improved through the installation of native vegetation. The species selected for this application are prolific and have dense, deep roots capable of stabilizing soils. Additionally, the plants provide shade that is important to maintain cool water temperatures necessary for existing fish populations.

In the upstream 6.6-mile project area, 58 sites encompassing over 2.75 miles of streambank were improved using one or more BMPs aimed at reducing streambank erosion. Stabilization techniques were identified on a site-specific basis and included j-hooks, cross-vanes, floodplain benches and streambank tapering. Native vegetation was also used extensively throughout this portion.

J-hook and cross-vane rock structures of varying size and length were constructed at appropriate locations to re-direct flow and reduce water velocity near erosion-prone streambanks. Banks that had already eroded to near-vertical slopes were tapered back or excavated into floodplain benches. Floodplain benches were used extensively where the channel had meandered away from its original location and continued to erode streambank consisting of fine sand.

Over 17,000 native plants and 6 acres of native seed were installed, including a variety of species selected specifically for the site conditions. In addition to bare root potted plants, portions of plants, called live stakes, were gathered from within the project area. Although this was more labor intensive than purchasing live stakes, using plants adapted to the local growing conditions ensured the highest potential for survival and growth.

The Board’s desire to provide a more stable drainage course for the Whitney Drain to prevent loss of property and protect roads and bridges has been achieved. More than 6 miles of streambed and side slopes have been stabilized while maintaining and improving the hydraulic capacity of the drain. The restoration structures are working as designed and the plants and grass are well established. Additional plantings will be installed on the downstream floodplain and adjacent valley walls in spring 2009. The natural design approach used is expected to substantially improve water quality and fishery habitat while reducing future sediment loading on Lake Huron.

Originally published in Innerview Vol. 22, No. 3, 2008

^Top